2015-02-20 18:36:57

by Robert Jarzmik

Subject: [PATCH v2] mtd: pxa3xx-nand: handle PIO in threaded interrupt

Change the handling of the data stage in the driver : don't pump data in
the top-half interrupt, but rather schedule a thread for non dma cases.

This will enable latencies in the data pumping, especially if delays are
required. Moreover platform shall be more reactive as other interrupts
can be served while pumping data.

No throughput degradation was observed, at least on the zylonite
platform, while a slight degradation was being expected.

Signed-off-by: Robert Jarzmik <[email protected]>
Tested-by: Maxime Ripard <[email protected]>
---
Since v1: use IRQF_ONESHOT per Maxime's comment
---
drivers/mtd/nand/pxa3xx_nand.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
index 96b0b1d..7ff5202 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c
@@ -569,11 +569,24 @@ static void start_data_dma(struct pxa3xx_nand_info *info)
{}
#endif

+static irqreturn_t pxa3xx_nand_irq_thread(int irq, void *data)
+{
+ struct pxa3xx_nand_info *info = data;
+
+ handle_data_pio(info);
+
+ info->state = STATE_CMD_DONE;
+ nand_writel(info, NDSR, NDSR_WRDREQ | NDSR_RDDREQ);
+
+ return IRQ_HANDLED;
+}
+
static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
{
struct pxa3xx_nand_info *info = devid;
unsigned int status, is_completed = 0, is_ready = 0;
unsigned int ready, cmd_done;
+ irqreturn_t ret = IRQ_HANDLED;

if (info->cs == 0) {
ready = NDSR_FLASH_RDY;
@@ -615,7 +628,8 @@ static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
} else {
info->state = (status & NDSR_RDDREQ) ?
STATE_PIO_READING : STATE_PIO_WRITING;
- handle_data_pio(info);
+ ret = IRQ_WAKE_THREAD;
+ goto NORMAL_IRQ_EXIT;
}
}
if (status & cmd_done) {
@@ -656,7 +670,7 @@ static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
if (is_ready)
complete(&info->dev_ready);
NORMAL_IRQ_EXIT:
- return IRQ_HANDLED;
+ return ret;
}

static inline int is_buf_blank(uint8_t *buf, size_t len)
@@ -1672,7 +1686,9 @@ static int alloc_nand_resource(struct platform_device *pdev)
/* initialize all interrupts to be disabled */
disable_int(info, NDSR_MASK);

- ret = request_irq(irq, pxa3xx_nand_irq, 0, pdev->name, info);
+ ret = request_threaded_irq(irq, pxa3xx_nand_irq,
+ pxa3xx_nand_irq_thread, IRQF_ONESHOT,
+ pdev->name, info);
if (ret < 0) {
dev_err(&pdev->dev, "failed to request IRQ\n");
goto fail_free_buf;
--
2.1.0

2015-02-28 09:16:17

by Brian Norris

Subject: Re: [PATCH v2] mtd: pxa3xx-nand: handle PIO in threaded interrupt

On Fri, Feb 20, 2015 at 07:36:43PM +0100, Robert Jarzmik wrote:
> Change the handling of the data stage in the driver : don't pump data in
> the top-half interrupt, but rather schedule a thread for non dma cases.
>
> This will enable latencies in the data pumping, especially if delays are
> required. Moreover platform shall be more reactive as other interrupts
> can be served while pumping data.
>
> No throughput degradation was observed, at least on the zylonite
> platform, while a slight degradation was being expected.
>
> Signed-off-by: Robert Jarzmik <[email protected]>
> Tested-by: Maxime Ripard <[email protected]>
> ---
> Since v1: use IRQF_ONESHOT per Maxime's comment

Pushed to l2-mtd.git. Thanks.

Brian